1. Field of the Invention
The invention is related to a combustion catalyst device for an internal combustion engine.
2. Description of Background and Relevant Information
The current problems of pollution generated by internal combustion engines are well known, whether such engines use fuels comprising gas, gas-oil, liquefied petroleum gas or compressed natural gas. Emissions emanating from these internal combustion engines are of several types, including unburnt hydrocarbons, carbon monoxides, nitrogen oxides and particles.
Systems already exist that make it possible to reduce certain emissions. For instance, injection systems associated with an electronic control allow for loop-through operations. In these systems, a probe placed in the exhaust makes it possible to analyze the gases and control the determination during intake, in association with a catalytic muffler and in manner so as to make it work by oxidation or reduction with the highest efficiency.
In practice, conventional catalysts can be started, as is the case for oxygen probes, only if the temperature of the exhaust gases and the catalytic structure are sufficiently high. Heating systems have been developed to be arranged immediately upstream of the catalysts, but such systems remain complex and expensive.
Unburnt hydrocarbon emissions result essentially from four factors:
a) the quality of the combustion itself; PA1 b) trapping of the hydrocarbons in the ullages of the combustion chamber which are very difficult to reach for complete burning; PA1 c) the phenomena of hydrocarbon absorption/desorption in the oil films; and PA1 d) the deposits capable of constituting substantial hydrocarbon retaining sources.
The trapping of the hydrocarbons in the ullages, which are difficult to reach for complete burning, constitutes the major source of unburnt gases that can reach up to 70% of the total evacuated hydrocarbons. The ullages are located between the first bearer and the cylinder and in the fire rings. The critical micro-volumes in the vicinity of the seats and valves are also a part of the ullages.
In the case of diesel engines, substantial quantities of unburnt particles are formed. If these particles are in hot zones, they will burn in the presence of oxygen. Those that could not burn are found in the exhaust conduits downstream of the combustion chambers.
In the case of natural gas, the emissions are essentially composed of methane, even with the use of catalytic converters. Indeed, the atoms of the methane molecule have very substantial bond strengths and the rate of combustion is low, which explains these high levels of emission.